Various cleanup/simplification in object-observe.js

Various cleanup/simplification in object-observe.js

The biggest change is the removal of the map wrapper objects: we now operate
directly on the observation weak map, since there are already Get/GetOrCreate/Set
functions for each info map. Various other small cleanups as well, including the
deletion of unnecessary forwarding functions and making use of standard macros.

R=arv@chromium.org, rossberg@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=24972

[adamk, 2014-10-28 14:49:55]

adamk@chromium.org changed reviewers:
+ arv@chromium.org, rossberg@chromium.org

[arv (Not doing code reviews), 2014-10-28 17:53:04]

LGTM

[rossberg, 2014-10-29 09:17:49]

lgtm

[adamk, 2014-10-29 10:32:34]

Committed patchset #1 (id:1) manually as 24972 (presubmit successful).